DUCTILE CRACKING SIMULATION OF BUTT WELD IN STEEL STRUCTURES UNDER MONOTONIC TENSION

摘要

Brittle fracture was first observed in many connections of welded steel buildings and bridges during the 1994 Northridge earthquake and the 1995 Kobe(Hyogoken-Nanbu)earthquake.It was found that ductile cracks preceding the brittle fracture played an important role.Therefore,it is necessary to study ductile cracking behaviors of welded steel structures to effectively prevent the following brittle fracture.In practice,most of steel structures are welded,and butt welding is commonly employed in many connections and members in steel structures.It is of great importance to investigate the ductile cracking behaviors of butt welds to obtain an accurate evaluation of welded steel structures.Former studies on butt weld are mainly qualitative,and quantitative studies have seldom been found.This paper aims to investigate the ductile cracking behaviors of butt-welded connections under monotonic tension using both experiments and numerical simulation.First,three butt-welded connections with weld beads were experimentally tested under monotonic tension.Secondly,a calibrated ductile fracture model was employed to simulate the ductile cracking behaviors of the connections.The experimental results indicated that minor ductile cracks first initiates at the weld toes,and necking occurred at the base metal,which induced strain concentration and final fracture of the connections.The numerical simulation can well capture the ductile crack initiation at the weld toes,and necking at the base metal.The load-displacement curves also agree well with the test results.